Background: Although CB 1 , the most abundant neuronal receptors, and CB 2 receptors are co-expressed in neurons, the CB 1 -CB 2 relationship is unknown. Results: CB 1 and CB 2 receptors form heteromers in neuronal cells and in the brain. Conclusion: Activation of either receptor leads to negative modulation of the partner receptor via heteromers. Significance: These heteromers may explain previous conflicting results and serve as therapeutic targets.

Dopamine and adrenergic receptor complexes form under a circadian-regulated cycle and directly modulate melatonin synthesis and release from the pineal gland.